Specificities of Ricinus communis agglutinin 120 interaction with sulfated galactose

Lectins are used extensively as research tools to detect and target specific oligosaccharide sequences. Ricinus communis agglutinin I (RCA(120)) recognizes non-reducing terminal β-D-galactose (Galβ) and its specificities of interactions with neutral and sialylated oligosaccharides have been well documented. Here we use carbohydrate arrays of sulfated Galβ-containing oligosaccharide probes, prepared from marine-derived galactans, to investigate their interactions with RCA(120). Our results showed that RCA(120) binding to Galβ1-4 was enhanced by 2-O- or 6-O-sulfation but abolished by 4-O-sulfation. The results were corroborated with competition experiments. Erythrina cristagalli lectin is also a Galβ-binding protein but it cannot accommodate any sulfation on Galβ.